1. Field of the Invention
This invention relates to an image sensing apparatus, such as a digital camera and digital video camera, which can correct a shake thereof.
2. Description of the Related Art
There has been known a mechanism provided in an image sensing apparatus such as a camera which can correct a shake of the apparatus resulting from a photographer. The conventional shake correcting mechanism includes a gyro as an example of shake detection sensors. The image sensing apparatus provided with such a shake correcting mechanism where an angular velocity of a shake of the image sensing apparatus is detected by the gyro, a shake amount of the image sensing apparatus is calculated based on the detected angular velocity, and a moving amount of an image sensor or a shake correction optical system is calculated based on the calculated shake amount so as to move the image sensor or the shake correction optical system depending on the calculated moving amount to thereby correct the shake of the image sensing apparatus.
A gyro is a device incorporated with a piezoelectric clement. The incorporated piezoelectric element is oscillated when a voltage is applied thereto. A symmetrical property of the piezoelectric element with respect to an axis of oscillation is collapsed by Coriolis action which acts on the piezoelectric element at a right angle to the direction of oscillation when an angular velocity is applied to the oscillating piezoelectric element. As a result of collapse of the symmetrical property, a distortion is generated in the oscillating piezoelectric element, and electric charges are generated therefrom. The gyro measures the angular velocity in terms of the generated electric charges.
The output voltage or detection sensitivity outputted from the gyro provided with the piezoelectric element has a dependency on a temperature characteristic inherent to the material composing the piezoelectric element. Accordingly, in the case of performing shake correction with use of a gyro, it is necessary to perform temperature correction considering the temperature characteristic of the piezoelectric element to secure the detection sensitivity of the gyro.
One approach to perform temperature correction taking into consideration of a temperature characteristic of a piezoelectric element is to provide a resistor for temperature correction so as to correct a measurement error resulting from a change in temperature, as disclosed in Japanese Unexamined Patent Publication No. 11-344344.
Shakes in an image sensing apparatus such as a camera are generated primarily at the time when a photographer depresses a shutter release button of the apparatus. Accordingly, shakes in pitch direction are generally larger than those in yaw direction of the apparatus.
In view of the above, a conventional image sensing apparatus has been designed to improve measurement precision of the gyro by increasing the number of samplings per unit time of shake detection in pitch direction compared with the number of samplings per unit time of shake detection in yaw direction, as disclosed in Japanese Unexamined Patent Publication No. 2001-290183.
In the former publication, however, since the resistor is additionally provided in the gyro to correct a measurement error resulting from a temperature change, a production cost rise concerning the gyro is inevitable.
In the latter publication, a change in the number of samplings per unit time between shake detections in yaw direction and in pitch direction necessitates a change in sampling frequency between the shake detections in yaw direction and in pitch direction, which makes the circuit configuration of the gyro complicated.